The invention relates to a pressure regulator for regulating the pressure of a fluid.
In particular, the invention refers to a pressure regulator that can be used in a gaseous fuel supply system, such as for example, natural gas, liquefied petroleum gas, hydrogen or similar, for regulating the pressure of the gaseous fuel flowing from a pressurized gaseous fuel source to an operating device, such as for example an internal combustion engine.
Mechanical pressure regulators are known, comprising a body inside which a regulation chamber is obtained.
Inside the regulation chamber a diaphragm or a piston is positioned, which divides this regulation chamber into a first chamber or upper chamber, and a second chamber or lower chamber.
The first chamber is connected to an environment at a reference pressure, for example, atmospheric pressure.
The second chamber comprises an inlet and an outlet for the gaseous fuel connected respectively to a source of gaseous fuel and to an operating device of gaseous fuel.
The known mechanical regulators furthermore comprise a valve for regulating a flow of gaseous fuel between the inlet and the outlet.
This valve is fixed to a first side of the diaphragm/piston, facing the second chamber, and is provided with a seat positioned in the second chamber, at the fuel flow inlet, between the inlet and outlet.
The known mechanical regulators furthermore comprise a spring positioned in the first chamber and fixed to a second side of the diaphragm/piston, facing the first chamber and opposite the first side.
During use, the spring exerts an elastic force on the diaphragm/piston, which acts on the valve by positioning and maintaining the valve at a certain distance from the seat in such a manner as to define a port through which a desired flow of gaseous fuel is allowed to flow.
In other words, by means of the diaphragm/piston, the spring positions the valve in a determined operating position which corresponds to a desired outlet pressure from the regulator. A limit of known mechanical regulators is that the outlet pressure varies with respect to a nominal pressure value in the operating range of the regulator, i.e. the outlet pressure changes with variation of an inlet regulator pressure and a required flow rate.
A further limit of known mechanical regulators is that they do not allow to regulate of the above-mentioned outlet pressure during operation, i.e. they work with a constant nominal outlet pressure which depends on the above-mentioned reference pressure.
In fact, this outlet pressure is determined by the operating position of the valve which depends on the elastic force exerted by the spring on the valve by means of the diaphragm/piston.
This elastic force depends on the features of the spring, on the preload and, in particular, on the elastic constant, and therefore, cannot be modified during operation.
A still further limit is that known mechanical regulators need periodic calibration in order to maintain and thus preserve the original performances.
This is due to the diaphragm which is subject to a time drift and permanent deformations.
Another drawback is that these regulators cannot be used at low temperatures, in the absence of a heat exchange between the gaseous fuel and a suitable heat source.
This is due to the diaphragm which, because of its sensitivity to temperature, becomes rigid at low temperatures.